Release agent for film-casting and embossing operations



Patented Oct. 30, 1945 RELEASE AGENT FOR FILM-CASTING AND EMBOSSING OPERATIONS Harry L. Boulton and Albert B. Savage, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan ' No Drawing. Application December 21, 1942,

Serial No. 469,696 Claims. (Cl. 106-179) M This invention relates to cellulose ether compositions and more particularly to 'a release agent therefor.

In the production of films or foil, and of embossed articles from cellulose ether compositions one of the difficulties encountered is in the Senaration of the finished article from the forming member, i. e. from the casting wheel or table, or from the die or press surface against which the surface of the article is formed. In the case of sheets, such as films or foils, undesirable sticking,tearing and stretching of the sheet frequently occurs when its removal from the surface is attempted. Easy release of the plastic composition is particularly necessary in the case of embossing operations, such as in the making of sound records, where patterns of intricatedetail are impressed in the record with a matrix, which is usually heated, and where extremely faithful reproduction of the matrix pattern must be maintained during separation of the pattern from the still heated matrix.

Because of these difficulties it has beco' e common practice to lncorporate'in the composition,

which is to be cast into sheets or embossed, a

lubricating agent which will facilitate removal of the article from the forming member. Among the substances which have been employed for the purpose are stearic acid, beeswax, carnauba wax, paraffin, aluminum palmitate, etc. Many of these substances, however, are unsatisfactory because they are compatible with the cellulose derivative over a wide range of proportions and do not remain on the surface of the composition in sulficient quantity to effect the desired degree of lubrication. Others of these materials tend to crystallize out of the composition upon aging thereby causing blushing, blooming or hazing of the article. Others impart a sticky or greasy feel to the surface of the article or render it so soft that it is easily scratched or marred. Still others cause embrittlement of the composition upon aging.

a heated die to secure faithful reproduction of the die surface.

These and related objects are readily accomplished by incorporating as a release agent in a cellulose ether film-forming or embossing composition from 0.5 to 12 per cent by weight of a higher polyglycol ester, 1. e. of an ester derived from a polyglycol having a molecular weight of, from about 2000 to about 5000. The cellulose ether composition containing the polyglycol ester may, but does not necessarily, contain one or more plasticizers such as those usuallv employed in preparing cellulose ether compositions for use in filmcasting or embossing operations. Due to the action of the release agent no difilculty is encountered in removing cast sheets from the casting surfaces used in forming them. Cleaning of the casting surfaces is substantially eliminated. Compositions containing the release agent of the invention are particularly adapted to having intricate patterns, such as decorative designs, sound tracks and the like, embossed in the surface of quently employed in cellulose ether lacquers to improve their adhesion to surfaces. When, however, only a minor proportion, e. g. from 0.5 to 12 per cent by weight of a corresponding higher p lyglycol ester, e. g. of polyglycol phthalate, etc., is included in the composition, ready release of the dried coating from smooth surfaces is obtained without distortion or tearing of the film. Films and the like prepared from compositions containing the polyglycol esters carry very little static electricity on their surfaces due, apparently, to the slightly hygroscopic nature of the esters.

It may be mentioned that a higher polyglycol ester may, if desired, alsobe used effectively as a release agent, particularly in embossing operations, by. dissolving it in a solvent, such as an alcoohl, a mixture of an alcohol and an aromatic I ether composition which may be embossed with hydrocarbon, etc., and coating the surface of the die with the solution. After the solution has dried, leaving a film of the ester on the' surface,

' sheets of cellulose ether compositions may be embossed with the coated die. Ready release ofthe die from the embossed sheet occurs. If desired. the solution of the release agent may be applied on the suriace of the sheet instead of on-the die. Certain of .the esters are somewhat soluble in water and aqueous solutions of these may be used to advantage.

Although any organo-soluble cellulose ether,

such as organo-soluble ethyl cellulose, methyl cellulose, butyl=cellulose and benzyl cellulose, may i assasoe Thus films cast from the composition may be lifted easily from the casting table and subsequently molded to paper in a heated press. The laminated product may be separated from the still hot press plates without marring oi the plastic surface. Previously i'ormed blanks for sound records may be embossed with a heated matrix to impress the sound track thereon and the finished record separated from the matrix with little or no intermediate cooling.

Certain advantages-of the invention may be seen from the following examples which are, howtypes and oi ethoxyl' from 2000 to 5000. One 01 these, known commer- Y cially as Carbowax 4000, and thought to be a polymerization product of ethylene oxide, is a' waxy solid having a molecular weightof about 3700 to 4000. The esters of the higher polyglycols may be prepared readily by reacting the polyglycols with organic acids or their anhydrides or with acid chlorides in accordance with known methods for the preparation of esters. Purification of the crude ester is not usually necessary. Either one or two hydroxyl groups ofthe polyglycol may be esterified. Among the higher polyglycol esters of value as release agents in cellulose ether compositions may be mentioned the maleate, mono-stearate, di-laurate, mono-oleate, di-oleate, monolaurate, phthalate, palmitate, succinate, ricinoleate, and butyrate of Carbowax and of polymerized propylene oxide. The esters of polycarboxylic acids and of high molecular weight/monocarboxylic acids, such as those having from to carbon atoms inclusive in the molecule, are 01.

particular value.

The higher polyglycol esters are efiective as filmand embossing-release agents in cellulose ether compositions when used in amounts of from 0.5 to 12 per cent by weight of the composition. In some instances, they are of limited compatibility, i. e. compatible to the extent only of from 3 to 10 per cent by weight with the cellulose ether. In such cases, it is preferable to use the esters in proportions below the limit of their compatibility. However, larger amounts may be used, if desired, although in such cases the finished film may be clouded in appearance.

As mentioned previously, plasticizers and other modifying agents may, if desired, be included in a the composition. The choice of a, plasticizer will depend to some extent on the particular'cellulose ether used and the properties desired in the finever, not to be construedas limiting.

Example 1 20 parts by weight of a composition consisting of '12 per cent of ethyl cellulose having an ethoxy content of about 45.5 per cent and a viscosity oi 50- centipoises, 20 per cent ,of .monophenyl di(o-xenyl) phosphate and 8 per cent of Carbowax maleate were dissolved in 80 parts of a solvent consisting of 70 parts by volume 01' toluene and 30 partsof ethanol. The solution was used in casting a film,'which was 0.002 inch thick when dry, on a polished chromium. plated panel. The lacquer was dried on the panel for 3 hours at about 70 F. and then for 2 hours at 125 F. and thenexposedffor 3 hours to air at 72 F. and a relative humidity of 50 percent. The dried and conditioned film, while stillon the panel, was cut into strips 1 inch wide with a sharp'knife. The "panel was then suspended with the strips in a similar 7. manner.

ished film. The art of plasticizing cellulose ether compositions toimpart to them desired properties is well known and need not be discussed here. Compatible resins may be added to alter the hardness of the composition as well as pigments, soluble dyes, and other modifying agents.

The composition of the invention may be prepared and articles formed therefrom in any convenient manner. Thus the cellulose ether and the polyglycol ester together, if desired, with a plasticizer, may be dissolved in a volatile organic solvent and film or foil then cast from the solution. After drying, the sheet may be removed readily from the casting surface without distortion or sticking. The polyglycol esters are eflfective release agents not only during film-casting operations, but also during subsequent embossing or laminating operations with the formed art c e.

vertical position. A single strip was separated at its upper end from the panel with a knife and,

' by means of a small clip and a fine wire a tray was suspended from the loose-end of the strip. Lead shot were then added to the tray until the strip peeled evenly-and slowly from the panel. The sum of the weights of the clip, wire and shot which just caused the strip to peel from the panel was 1.8 grams. The surface of the strip was uninjured during its removal. Byway of comparison a composition consisting of 80 parts by weight of the same ethyl cellulose and 20 parts of monophenyl di(o-xenyl) phosphate was tested in a The total weight required in this case was 2'70 grams. In still another comparative test unesterified Carbowax was substituted for the Carbowax maleate. A weight of 440 grams was required'in this case.

The Carbowax maleate used in thef above' example was prepared ,by stirring 2 00 parts by weight of "Carbowax 4000" and 6 parts of maleic anhydride together at C. for 2 hours. The reaction product was then used as a release agent without purification.

Example 2.

of Carbitol maleate. 1

Example 3 -A thin film was solvent-cast-as in Example 2 from a composition consisting of 48 percent by weight of ethyl cellulose having an ethoxy conwe of 46 percent and a viscosity of tenuaaeaaoepoises, 35 percent oimonophenyl di(oxe'nyl) Y phosphate, per cent of di(p-tert.-butyl-phenyl) mono('5-tert.-butyl-2-xenyl)- phosphate and 2 per cent of Carbowax phthalate. The film was separated from the casting'sur'face easily and without distortion. ,The film was then molded to paper between polished press plates at 300 F. and 1000 pounds per square inch pressure. Thep fess was opened and the laminated product removed without cooling. The hot laminated product Example 4 I a: parts by weight or ethyl cellulose-having showed no tendency to stick to the press plates;

an ethoxy content of about 45 per cent and a I viscosity of about 60 centlpoise's, 6 parts of di(p-x tert.-butyl-phenyl) mono (5-tert.-butyl- 2-xenyl) phosphate, 3 parts. of monophenyl di(o-.xenyl) phosphate and 1 part of Carbowax phthalate were dissolved in 80 parts of a mixture, consisting of 80 parts by volume of benzene and 3 upon being played reproduced the original sound faithfully.

We claim:

1. A composition includin an organo-scluble cellulose ether, a plasticizer for the cellulose other and, as a release agent, from 0.5 to 12 per cent by weight of a polyglycol ester of an organic carboxylic acid, said polyglycol having a weight of from 2000 to5000.

2'. A composition including ethyl. cellulose, a plasticizer for the ethyl cellulose and, as a release agent. from 0.5 to 12 per cent by weight of apolyglycol ester otzan organic carboxylic acid, said no yelycol having a molecular weight of from 2000 to 5000;

r a. A composition'including ethylcell'ulose, a

plasticizer for theethyl cellulose and, as a release agent, from 0.5 to 12 per cent by weight of a 'polyethyleneglycol, ester of an organic car- 20 .bomlic' acid, said polyethylene-glycol having a molecular weight of from 2000 to 5000.

parts of methanol. 2 parts by weight of Titanox AA (a white pigment) and 1 part of Toluidine Toner (a red coloring agent) were added and a illm' about 0.015 inch thick was solvent-cast from the mixture. The dried illm was readily removed from the casting surface without sticking. A 0 sound track was impressed simultaneously. in each side of a circular section of the film. The matrices.

. plasticizer for the ethyl cellulose and, as arelease used in forming the sound track were heated to about270 F. and a pressure of 1000 pounds per square ch was used. After slight cooling,-

of the mat ces, the embossed film was removed from the press without sticking. The record,

4..A composition including ethyl cellulose; a'

agent, from 0.5 to'12 per-cent by weight of a polyethyleneglycol maleate, said polyethylene-"' glycol having a molecular weight of' from 2000-to HARRYL. Bonn-roar.-

I ALBEliT B. SAVAGEI I molecular 

